The present invention relates to the field of survival radios and, more particularly, to a search and rescue system consisting of a primary interrogation, decoding and display unit and a plurality of portable beacon radios.
Radio based search and rescue systems are in common usage in aviation. Personal survival radios (PSR) are standard equipment for military pilots and for others who routinely carry out missions in remote locations.
Most search and rescue systems are based on determining the position of a downed aviator's emergency emitter, customarily a beacon radio, by means of various types of direction finding and range finding devices that detect its signal. Early versions of such technology required the radio beacon signal to be transmitted continuously in order to calculate range and bearing. Later versions employed GPS technology to enable the beacon to produce its own location information. GPS technology does not require that the radio transmit continuously. Rather, the searching transceiver may periodically prompt the PSR to transmit GPS generated location information. Such prompting, obviating the need for continuous signal transmission, provides many benefits, particularly in combat environments where disclosure of the survivor's position may expose him to harm from enemy forces.
The technology of survival radios is well known in the art. U.S. Pat. No. 5,847,679 assigned to Motorola, Inc., reflects an airborne GPS based system that incorporates “over the horizon” extended range capability. U.S. Pat. No. 6,011,510, also assigned to Motorola, Inc., teaches a PSR as an element of an airborne search and rescue system which transmits a GPS derived location signal. Such technology, which was specifically conceived and designed for military and paramilitary use, is incorporated into Motorola, Inc.'s AN/PRC-112 PSR. This radio, and others like it, have wide application in aviation for rescuing downed airmen.
The systems referred to above are designed to be installed within aircraft. They allow an airborne searching transceiver to send interrogation messages to an identified PSR. Upon receiving such a message, the PSR will respond with location information and, in some cases, a text message. Such systems use the transceiver of the aircraft in which they are installed and therefore communicate on the UHF frequencies utilized by the avionics of the aircraft. Such systems are not portable, versatile nor capable of various applications.
A further limitation of such systems is the inability of one PSR to communicate with another PSR. This feature would be particularly helpful when more than one airman from the same aircraft is down within a relatively small geographic area and contact between them would enhance their chances of survival.
Accordingly, there is a need for a simple, portable, versatile and inexpensive search and rescue system that incorporates a number of small hand-held units that may communicate among themselves.